The present invention relates to semiconductors, and more specifically, to semiconductor fin patterning.
Device scaling drives the semiconductor industry, which reduces costs, decreases power consumption, and provides faster devices with increased functions per unit area. Improvements in optical lithography have played a role in device scaling. However, optical lithography may have limitations for minimum dimensions, which are determined by the wavelength of the irradiation.
Directed self-assembly (DSA) is an alternative method for forming periodic structures, such as one-dimensional arrays of semiconductor line structures. In order to convert the array of semiconductor line structures into semiconductor fins, portions of the semiconductor line structures are etched away by employing lithographic stacks. DSA of block copolymers (BCPs) employs a topographical or chemical guiding pattern to direct the BCPs into a desired morphology at a pre-determined location. BCPs are made up of two or more chemically distinct homopolymers covalently bonded at one end. Such a material is capable of micro-phase segregation under proper annealing conditions, i.e., self-assemble into periodic structures with critical dimensions of tens of nanometers. The BCP material properties control the feature size and uniformity of the resulting structures.
In one example, di-block copolymers, for example polystyrene (PS)/poly(methyl methacrylate) (PMMA), BCPs can be used to pattern fins. The PS and PMMA blocks define where the fins and spaces between the fins are arranged, respectively. Reactive ion etching (RIE) may then remove the PMMA block and reduce the critical dimensions (CD) of the fins to achieve the final fin CD.